Elphel cameras are free software and open hardware cameras.
The cameras run Linux.
The cameras have several interfaces -- 10/100 Ethernet, USB, IDE, RS-232, etc.
It uses a FPGA for video processing and video compression.
More information here at Open Circuits: Elphel camera; and at the Elphel wiki.

The Balloon project has produced Balloon3, a high-performance ARM board designed for use by OEMs and Higher education. Spec is PXA270 (583Mhz), FPGA or CPLD, 1GB flash, 784MB RAM, USB (master, slave, OTG), CF slot, expansion bus, 16-bit bus, I2C, LCD, serial, audio. Very low power in CPLD confiuguration. Small, light. Various add-on boards: VGA LCD driver, robot motor driver+A/D, digital IO. Released under the Balloon Open Hardware license, which allows anyone to manufacture and for people to make derivatives. The expansion bus allows balloon to be used as the computing component for various special-purpose devices.

LART -- an open license StrongARM based tiny SBC

"All CAD files required for building LART are available under the closest we could get to an Open/Free Hardware License."
The link in the Linux Devices article no longer works; the most recent link is http://www.lartmaker.nl/ .
75 mm x 100 mm.

Gumstix

These motherboards are based on a SBC, are inexpensive, and have RAM/Flash on board. The Modules include USB interface (gadget mode and host mode)
and have things like GPIO and LCD module interface. They have Marvel PXA270, TI's OMAP3503, etc. Very cool site.
Some expansion boards are open hardware.
Gumstix wiki.